Oxidation and ammoxidation catalyst

ABSTRACT

An oxidation/ammoxidation catalyst contains the elements antimony, uranium, iron and tungsten in a catalytic active oxidized state.

United States Patent [1 1 OXIDATION AND AMMOXIDATION CATALYST Tao P. Li, Chesterfield, Mo.

Assignee: Monsanto Company, St. Louis, Mo.

Filed: Jan. 2, 1973 Appl. No.: 320,372

Inventor:

US. Cl. 252/456; 252/458; 252/459; 252/467; 252/470; 260/465.3

Int. Cl B0lj 11/22 Field of Search 252/458, 467, 470, 456; 260/4654 References Cited UNITED STATES PATENTS 8/1965 Callahan et al. 252/467 X Primary ExaminerWinston A. Douglas Assistant Examiner-W. J. Shine Attorney, Agent, or Firm-Paul L. Passley 57 ABSTRACT An oxidation/ammoxidation catalyst contains the elements antimony, uranium, iron and tungsten in a catalytic active oxidized state.

6 Claims, No Drawings OXIDATION AND AMMOXIDATION CATALYST BACKGROUND OF THE INVENTION This invention relates to an improved oxidation and- /or ammoxidation catalyst system containing the elements antimony, uranium, iron and tungsten and to a method for preparing such catalyst system.

It is well known that olefins can be oxidized to oxygenated hydrocarbons such as unsaturated aldehydes and acids, for example, acrolein and methacrolein, acrylic and methacrylic acid. It is also well known that olefins can be ammoxidized to unsaturated nitriles such as acrylonitrile and methacrylonitrile. The value of such oxygenated hydrocarbons and unsaturated nitriles is generally well recognized with acrylonitrile being among the most valuable monomers available to the polymer industry for producing useful polymeric products.

Various catalytic processes are known for the oxidation and/or ammoxidation of olefins. Such processes commonly react an olefin or an olefin-ammonia mixture with oxygen in the vapor phase in the presence of a catalyst. For the production of acrolein and acrylonitrile, propylene is the generally used olefin reactant and for the production of methacrolein and methacrylo nitrile, isobutylene is the generally used olefin reactant.

A catalyst system composed of the oxides of antimony and uranium and the oxidation and ammoxidation of olefins using such catalyst has been described in U.S. Pat. Nos. 3,198,750 and 3,308,151. These patents describe preparation of the catalyst by precipitation wherein the oxides of the elements are contained in a slurry which is filtered to remove soluble salts and recover the catalytic components as the filter cake.

In the catalytic oxidation and/or ammoxidation of olefins, the commercial utility of a catalyst system is highly dependent upon the cost of the system, the con version of the olefin and the yield of the desired product. In many cases a reduction in the vcost of a catalyst system in the order of a few pennies per pound or a 1% increase in the yield of a desired product represents a tremendous commercial economical savings. Accordingly, research efforts are continuously being made to define new or improved catalyst systems and methods of making new and old catalyst systems to reduce the cost and/or to upgrade the activity and selectivity of such catalyst systems in particular processes.

SUMMARY This invention is directed to an improved catalyst system containing the elements antimony, uranium, iron and tungsten having commercial activity and selectivity for the catalytic oxidation and/or ammoxidation of olefins and to an improved method of making such catalyst system.

Accordingly, typical objects of this invention are to provide: 1 an improved oxidation and/or ammoxidation catalyst system containing oxygen, antimony, uranium, iron and tungsten, (2) an improved process for the preparation of a catalyst system containing oxygen, antimony, uranium, iron and tungsten, and (3) an improved olefin conversion process.

Other objects, aspects and advantages of this invention will become apparent to those skilled in the art upon further study of this disclosure and the appended claims.

In accordance with this invention, a new oxidation/ammoxidation catalyst system based on the elements antimony, uranium, iron and tungsten is provided. The elements are in combination with oxygen and may exist as individual oxides or as complexes of two or more of the elements and oxygen as a combination of oxides and complexes. The atomic ratio of the elements present in the catalyst system may vary over a wide range. Generally speaking the catalyst may be defined by the following empirical formula:

Sb U Fe W O wherein a is 1-10, b is 0.01 to 1, C is 0.01 to 1, dis 0.001 to 0.1 and e is a number taken to satisfy the average valences of the Sb, U, Fe and W in the oxidation states in which they exist in the catalyst.

The catalyst can be prepared starting with individual oxides or sulfates of the elements. A preferred method of preparing the catalyst is to combine the oxides or sulfates of the elements with sulfuric acid. When antimony sulfate is used as a starting material, it can be added to water wherein sulfuric acid is obtained. Nitric acid is used to oxidize the sulfate salts of the elements or to further oxidize the oxides of the elements. After the acid mixture has digested, the pH of the mixture is adjusted to about 8 followed by filtration.

After filtering the mixture, the filter cake can be dried at a temperature of from about C to about 180C. A suitable drying temperature is about C. However, the drying can be obtained at higher temperatures such as up to about 650C. The time required for drying the filter cake can range from an hour up to about 64 hours. Obviously, the drying temperature selected will dictate the required drying time with the lower temperature requiring the longer time. Also, the filter cake may be dried at different temperatures, for example at 110C for from 2 to 64 hours and then at a temperature of from about 250C to about 650C for from 2 to 24 hours.

After the filter cake is dried, it is further heated at an elevated temperature to obtain the active catalytic form of the elements. This calcination of the catalyst is conducted at a temperature in the range of from about 500C to about 1,150C. The time for calcination can vary and depends upon the temperatures employed. Generally, a time period of 2 to 24 hours at the designated temperatures is sufficient. The calcination may be conducted in the presence of oxygen (air); however, the catalyst may also be made active by calcining it in the absence of oxygen, such as in a nitrogen atmosphere.

The catalyst can be employed without support, and will display excellent activity. It also can be combined with a support, and preferably at least 5% up to about 90% preferably 5 to 50%, of the supporting compound by weight of the entire composition is employed in this event. Any known support materials can be used, such, for example, silica, alumina, zirconia, alundum, silicon carbide, alumina-silica, and the inorganic phosphates, silicates, aluminates, borates and carbonates stable under the reaction conditions to be encountered in the use of the catalyst.

The improved catalyst of this invention exhibits exceptional utility in the conversion of olefins with or without the presence of ammonia. The olefins employed as reactants for conversion by the catalyst of this invention may be open chain as well as cyclic and propylene (C ll converted mols C H in feed mols C l-1 in effluent mols C H in feed propylene to acrylonitrile tene-l, cyclopentene, cyclohexene, and the like. Parmols C H in feed ticularly, when the catalyst of this invention is used as merely an oxidation catalyst, it is particularly adapted The apparatus employed in carrying out the runs in to the conversion of propylene to acrolein and isobutylthis example is a fluidized bed type reactor. The reactor ene to methacrolein. Of course, mixtures of olefins may consists of a 14 mm. inside diameter 96% quartz glass be employed and mixtures of olefins with other hydrotube fitted at the bottom with a fritted disc for supportcarbons are applicable to the process of this invention. ing a catalyst bed of up to 50 ml. in volume and fitted When the catalyst of this invention is to be used as an at the top with another fritted disc to remove entrained ammoxidation catalyst, the olefins as aforestated are catalyst from the reactor effluent. A thermowell of 4 applicable. However, the catalyst of this invention is mm. outside diameter 96% quartz glass extends particularly adapted to the conversion of propylene 15 through the center of the catalyst bed to the fritted with ammonia and oxygen to acrylonitrile at 250C to disc. The reactor tube is jacketed with a larger tube in 650C. which sand is fluidized for providing even heat distribu- The molar ratio of oxygen to the olefin in the feed tion. The entire reactor assembly is placed in a conwill generally b in the range f0 5;1 t 4;] wi h a trolled, hinged tube furnace. The reactant gases are ferred ratio being 1:1 to 3:1. The molar ratio of ammo- Premixed and healed 0 ut C f r ntering nia to olefin in the feed will nerall b i th range the bottom of the reactor through a single inlet tube. of 0.5:1 to 5:1 and preferably slightly over the stoichio- The ffluent g s from h reac or r heate to premetric ratio of 1:1 ammonia:olefin will be employed. vent condensation prior to chromatographic analysis.

Wh1le amrnoma is most generally employed as the n1- EXAMPLE I trogen prov1d1ng compound, other nitrogen contammg materials m b em l d whi h decompose to Five catalyst systems composed of antimony, uraduce reactive nitrogen under the reaction conditions. Ilium, iron and tungsten are P p y adding anti A source f Oxygen, pure or i admixture i h i mony and uranium oxides and iron sulfate to a sulfuric may be employed in the process of this invention. Air i Solution Co g 33 gr of 98% 2 4 and is a satisfactory source of oxygen for use in thi i 200 ml. of water at about 80C. The mixture is stirred non, for about three hours. Nitric acid is added to the mix- The catal st tem of thi i venti can b d ture which is then heated for one to two hours to fur geously employed for synthesizing styrene from eth lther oxidize the elements. After cooling the mixture the benzene and oxygen, butadiene from butenes and my pH is adjusted to about 8 with ammonium hydroxide. gen, acrolein or methacrolein from propylene or isobu- 35 The mixture is allowed to digest about 16 hours. After tylene and oxygen, acrylonitrile or methacrylonit il digestion the mixture is filtered and the precipitate is from propylene 0r igobutylene, ammonia and oxygen, washed with water. The precipitate is mixed With silica isoprene from 2-methyl butene-2 and oxygen, and 2- sol (Ludox AS) and either ammonium tungstate or cyano-l,3-butadiene from 2-methyl butene 2 or isophosphotungstic acid. This mixture is evaporated to prene, ammonia and oxygen. dryness and further dried at about 110C for about 16 hours. The resulting catalyst is calcined at 900C for 16 DESCRIPTION OF PREFERRED EMBODIMENTS hours. The quantities of the various components used The following Examples are presented as illustrative in making catalyst systems are given in the following of the invention and, as such, are not intended to be re- Table l.

TABLE I COMPONENT CAT.A CAT.E CAT.C CAT.D CAT.E

Sb ongrams) 56.5 56.5 56.5 54.7 54.7 U 01, (grams) 18.25 18.25 14.0 14.0 F3504 .7H2O (grams) 18.12 18.12 36.24 27.8 27.8 4)'i 7 24' 6H O(grams) 0.7 P,0 ,.24wo 5lH O(grams) 1.43 .72 .83 .83 Silica sol (Ludox AS) (grams) 58.7 58.7 58.7 58.7 93.0

ATOMIC RATIO W 310.5. 310.5; 3.01; 2.50.33 2.50.33

0.5: 0.5: 0.02 0.66: 0.66: 0.02 0.04 0.02 0.02 SiO 17 17 19.5 17.5 25

strictive upon the specific materials, quantities and operation variables specifically set forth therein. LE ll As used in the examples, the following terms have the following definitions:

Four catalyst systems made according to the general procedure of Example I are used in the conversion of propylene and ammonia to acrylonitrile using the apparatus previously described. The feed composition in these comparative runs is 8.5% ammonia, 7.4% propy- The above example shows that various atomic ratios of antimony in the catalyst system of this invention are useful.

EXAMPLE IV lene, 17.7% oxygen and 66.4% helium. In each run the 5 temperature is about 470C and the pressure is atmospheric. Other process data and the results are given in Three Catalyst Systems made according to the general T bl 11 Th Catalysts are id tifi d procedure of Example I are used in the conversion of A sb uw propylene and ammonia to acrylonitrile using the appa- B Sb F W l ratus previously described. The feed composition in C Sb .,l,I Fe these comparative runs is 8.5% ammonia, 7.4% propy- D Sb;,U Fe W lene, 17.7% oxygen and 66.4% helium. In each run the TABLE II Catalyst A B C D Catalyst Weight (grams) 30 30 40 40 25 30 Contact Time* (gm.sec./ml.) at STP 6 6 8 8 5 5 6 6 Percent Propylene Converted 94.2 95.1 98.0 97.7 99.7 96.5 95.3 96.4 Percent Propylene to Acrylonitrile 59.9 63.9 66.7 64.8 68.3 78.8 78.5 79.9

*Contact time determined as temperature is about 470C and the pressure is atmospheric. Other process data and the results are given in Feed How we (mL/Sec') at STP Table IV. The catalysts are identified as: 30 A sb U Fe w 17.5% SiO The above example shows the improved ammoxidation 2 22 8 1? -& 6 activity of the four component catalyst system of this e03 0 1 2 invention compared with three component catalysts. TABLE IV EXAMPLE I Catalyst A B C Three catalyst systems made according to the general procedure of Example I are used in the conversion of wcght 25 25 25 25 25 25 propylene and ammonia to acrylonitrile using the appa- Coma Time* ratus previously described. The feed composition in (g -l 5 5 5 5 7 7 these comparative runs is 8.9% ammonia, 8.5% propy- 212; Propylene lene, l7.4% oxygengand 65.2% helium. In each run the c v l 917 9 5 9 9 & 7 tern erature is about 470C, the pressure is atmo- Percent may we sphd ric, 30.0 grams of catalyst is used and the contact to Acrylommle time is 6 gm.sec./ml (at STP). Other process data and the results are given in Table III. The catalysts are identified as:

*Contact time determined as Weight of Catalyst (grams) A 2.5 0.33 0.66 0.04 Feed Flow rate (mL/sec.) at STP B a oas ass am C as asa oss am The above example shows that various atomic ratios of uranium and iron in the catalyst system of this inven- TABLE III tion are useful.

EXAMPLE V Catalyst A B C Two catalyst systems made according to the general procedure of Example I are used in the conversion of percent Pmpylene propylene and ammonia to acrylonitrile using the appa- Converted 92.8 95,2 91.9 91.4 88.3 89.8 Percent Propylene ratus previously described. The feed composition in Acrylmilrilc 796 these comparative runs is 8.9% ammonia, 8.5% propylene, 17.5% oxygen and 65.1% helium. In each run the temperature is about 490C and the pressure is atmospheric. Other process data and the results are given in *Contact time determined as Weight of Catalyst (grams) Feed Flow rate (ml/sec.) at STP Table V. The catalysts are identified as:

A sb u 1=e w 25% SiO B Sb U Fe w 50% Si0 TABLE V Catalyst A B Catalyst Weight (grams) 30 30 30 30 Contact Time* (gm.secJml.) at STP 6 6 6 6 Percent Propylene Converted 94.0 93.7 91.9 91.4 Percent Propylene to Acrylonitrile 76.5 75.9 75.6 73.6

*Contact time determined as Weight of Catalyst (grams) Feed Flow rate (ml/sec.) at STP This example shows that various percentages of support material in the catalyst system of this invention are useful.

EXAMPLE Vl Four catalyst systems prepared according to the general procedure of Example I are used in the conversion of propylene and ammonia to acrylonitrile using the apparatus previously described. The feed composition in these comparative runs is 8.9% ammonia, 8.5% propylene, 17.4% oxygen and 55.2% helium. In each run the temperature is about 470C and the pressure is atmospheric. Other process data and the results are given in Table VI. The catalysts are identified as:

C zs oaa ass ons 25% 2 65.1% helium, all on a volume basis, at a temperature of 500C and atmospheric pressure.

EXAMPLE VII] The antimony-uranium-iron-tungsten catalysts of Example I are used in the conversion of propylene to acrolein using the apparatus previously described. Acrolein is obtained using each catalyst with a feed composition of 7.0% propylene, 11.0% oxygen and 82% helium, all on a volume basis, at a temperature of 500C and atmospheric pressure.

It will be obvious to persons skilled in the art that various modifications may be made in the improved catalyst and process as described in this application. Ac cordingly, it is intended that all such modifications which reasonably fall within the scope of the appended claims are a part hereof.

What is claimed is:

l. A catalyst system comprising the elements antimony, uranium, iron and tungsten in a catalytic active oxidized state represented by the formula:

wherein A is 1 10, b is 0.01 1, c is 0.01 to 1, d is 0.001 to 0.1 and e is a number taken to satisfy the average valences of the Sb, U, Fe and W in their catalytic active oxidation states, said catalyst system being formed by heating oxides or sulfates of said elements at a temperature in the range of from about 500C. to 1,150C. for a time sufficient to form said catalytic active oxidation states.

2. The catalyst system of claim 1 carried on a support.

3. The catalyst system of claim 1 prepared by forming D Sb U Fe W 30% SiO 35 a mixture of oxides or sulfates of antimony, uranium TABLE VI Catalyst A B C D Catalyst Weight (grams) 30 30 3O 30 30 30 30 30 Contact Time* (gm.sec./ml.) at STP 6 6 6 6 6 6 6 6 Percent Propylene Converted 92.8 95.2 95.6 91.8 92.5 88.5 94.8 91.0 Percent Propylene to Acrylonitrile 74.6 76.6 78.3 64.4 75.2 71.3 74.9 70.9

*Contact time determined as Weight of Catalyst (grams) Feed Flow rate (ml/sec.) at STP The above example shows that various atomic ratios of the tungsten in the catalyst system of this invention are useful.

EXAMPLE VII and iron in sulfuric acid, digesting the resulting mixture, adjusting the pH to about 8, filtering the mixture, mixing the filter cake with ammonium tungstate or phosphotungstic acid and evaporating the filter cake mixture to dryness, then heating the dried filter cake mixture at a temperature of from about 500C to about 1,150C to form said active compound.

4. The catalyst system of claim 3 wherein said mixture is formed from Sb O U 0 and FeSO .7H O.

5. The catalyst system of claim 3 wherein the mixture is oxidized with nitric acid prior to the pH adjustment.

6. The catalyst system of claim 2 wherein the support is silica. 

1. A CATALYST SYSTEM COMPRISING THE ELEMENTS ANTIMONY, URANIUM, IRON AND TUNGSTEN IN A CATALYTIC ACTIVE OXIDIZED STATE REPRESENTED BY THE FORMULA:
 2. The catalyst system of claim 1 carried on a support.
 3. The catalyst system of claim 1 prepared by forming a mixture of oxides or sulfates of antimony, uranium and iron in sulfuric acid, digesting the resulting mixture, adjusting the pH to about 8, filtering the mixture, mixing the filter cake with ammonium tungstate or phosphotungstic acid and evaporating the filter cake mixture to dryness, then heating the dried filter cake mixture at a temperature of from about 500*C to about 1,150*C to form said active compound.
 4. The catalyst system of claim 3 wherein said mixture is formed from Sb2O3, U3O8 and FeSO4.7H2O.
 5. The catalyst system of claim 3 wherein the mixture is oxidized with nitric acid prior to the pH adjustment.
 6. The catalyst system of claim 2 wherein the support is silica. 